Wet Exhaust, Wet Plug [Update] [Now with delicious video]

MattIn11225

MattIn11225

New Member
Good evening princes of the ton, Kings of Cafe.

Maybe someone can lend me their experience. I've got a 1972 CB350 K4, 14,400 miles on the odo. I've had it for a few months so far. When I first got it, it ran rather rough, with the right cylinder firing intermittently, or possible not at all. Took it to a local buddy who helped with the carbs, which had been out of sync, as well as some other issues. At any rate, it took care of the left cylinder, which is now firing strong.

I took her out the other day, and it smelled rather strongly of fuel. When I got home, I noticed the left exhaust looked quite wet. My first thought was water vapor from the combustion, but I pulled the plugs anyway. The right side plug is golden brown and delicious. The left one was very wet, and smelled vaguely of fuel, but it looked dark, like oil. I did a compression check, 180 PSI on both cylinders, so I don't think it's oil coming up from below the pistons.

Could this be caused by an overly rich condition? Any advice?
 
Re: Wet Exhaust, Wet Plug

Addendum:

The airbox and carbs are stock. The PO added slash-cut mufflers, full sized to me eyes.
 
Re: Wet Exhaust, Wet Plug

Make sure your timing is set correctly, points are good and plug gap is correct.
 
Re: Wet Exhaust, Wet Plug

Also... Pull the plug boots off, and cut about a 1/2" from the plug wire. Reattach the boots and stick them back on the plugs.
 
Re: Wet Exhaust, Wet Plug

Points and timing were set within the past few weeks. Plugs changed, right plug looks good, left is looking wet and blackened, definitely fouled.
 
Re: Wet Exhaust, Wet Plug

Bump on this, any thoughts? To rehash:

Wet residue in left pipe, right is clean.
Left plug is black and a bit wet. Also seeing liquid on threads of left plug when removed. Right plug looks just right.
I've been recently told that left pipe is throwing greyish smoke. It's not pouring out, but definitely visible.

Both cylinders are showing roughly 180 psi of compression. Points are set and clean, timing is stop on. I charged the battery, installed new plugs (properly gapped) and ran it for 20-30 miles, still showing the same symptoms.

Not really sure where to start looking.
 
Re: Wet Exhaust, Wet Plug

MattIn11225 said:
Bump on this, any thoughts? To rehash:

Wet residue in left pipe, right is clean.
Left plug is black and a bit wet. Also seeing liquid on threads of left plug when removed. Right plug looks just right.
I've been recently told that left pipe is throwing greyish smoke. It's not pouring out, but definitely visible.

Both cylinders are showing roughly 180 psi of compression. Points are set and clean, timing is stop on. I charged the battery, installed new plugs (properly gapped) and ran it for 20-30 miles, still showing the same symptoms.

Not really sure where to start looking.
Click to expand...

might be a valve out of que. When you do a compression test, you check for compression. The compression you measure does not tell you at which point it's made. Valves could be a little tight or loose, making compression at some point, but not at TDC-F. Check and report ;)
Worn valveguide seal could also be the problem.
 
Re: Wet Exhaust, Wet Plug

If it's oil it's probably a valve guide seal - but I don't remember if that motor had such a thing.

Assuming it's fuel the possibilities include:
Wrong float level
Sunk float
Pilot jet that's been cleaned with wire and is now oversized
Air/mixture screws out of adjustment.

I'd start by checking the screws and then I'd beg borrow or steal a carb synch tool and synch the carbs
If that doesn't fix it, the carbs have to come off to have float levels set properly.
 
Re: Wet Exhaust, Wet Plug

teazer said:
If it's oil it's probably a valve guide seal - but I don't remember if that motor had such a thing.
Click to expand...

me neither, but it does sound like it's coming from the skies ;)
 
Re: Wet Exhaust, Wet Plug

An update:

I tore apart the carbs today, checked to make sure everything was ok, set the fuel mixture to factory spec. The left cylinder now fires, and it seems to be pretty stead when it's running solo. The right cylinder will hold a very rough idle on its own, lots of pulsing 100-300 rpm every few seconds, and when they run together, the whole thing sounds super rough and shaky. New Thoughts?
 
Re: Wet Exhaust, Wet Plug [Update]

I've uploaded two videos onto Youtube, linked below.

http://www.youtube.com/watch?v=slaEDPKRse8&feature=youtu.be


http://www.youtube.com/watch?v=ShBGb02N3zA&feature=youtu.be

The first video shows both cylinders firing. The left sounds fine, to my ears, and runs smooth at about 900 RPM when it's on it's own. The right cylinder is the one that is sounding like it's missing, and the one that seems to be holding RPM when the throttle is pulled. The second video is the right cylinder on its own, it's eratic, sounds like it's missing the occasional combustion, and clearly is hanging when I give throttle. At the end of the video, the motor almost dies, but then recovers slightly with no input from the throttle.

I had the carbs apart today because the left cylinder was not firing at idle. It obviously is not an issue any more. The carbs are synced, using the "listen very closely to the idle screws coming down together method." Does this sound like anything in particular to anyone?
 
how about fresh plugs and caps? Running one coil? change plug caps and see if problem switches to the other side.
 
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